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Organization of Course
INTRODUCTION
1. Course overview
2. Air Toxics overview
3. HYSPLIT overview
HYSPLIT Theory and Practice
4. Meteorology
5. Back Trajectories
6. Concentrations / Deposition
7. HYSPLIT-SV for
semivolatiles (e.g, PCDD/F)
8. HYSPLIT-HG for mercury
Overall Project Issues & Examples
9. Emissions Inventories
10. Source-Receptor Post-
Processing
11. Source-Attribution for Deposition
12. Model Evaluation
13. Model Intercomparison
14. Collaboration Possibilities
For the atmospheric fate of air toxics,
everything depends on vapor-particle partitioning
vapor-phase
pollutant
example:
Hexachloro-
benzene
(HCB)
semi-volatile
pollutant
example:
2,3,7,8-TCDD
low volatility
pollutant
example:
OCDD
particle-phase
pollutant
example:
Cadmium
Atmospheric Chemistry Wet and Dry Deposition
For the atmospheric fate of air toxics,
everything depends on vapor-particle partitioning
vapor-phase
pollutant
example:
Hexachloro-
benzene
(HCB)
semi-volatile
pollutant
example:
2,3,7,8-TCDD
low volatility
pollutant
example:
OCDD
particle-phase
pollutant
example:
Cadmium
Atmospheric Chemistry Wet and Dry Deposition
If the local atmospheric relative humidity is above 70-80%, particles
become droplets and this affects partitioning, chemistry, and deposition
acenapht hylenehept achlor
aldrin4,4'-met hy lene bis(2-chloroaniline)acenapht hene
pyrenetetraethy l leadmethoxy chlor
bis (tributy ltin) oxideanthracene
f luoranthenechrysene
benz [ a ] ant hracenenaphthalene
benzo [ j ] f luoranthenebenzo [ b ] f luorant hene
dimethy l m ercuryphenanthrene
benzo [ e ] py renebenzo [ a ] py renef luorene
endrindieldr in
monomethy l mercury chloridep,p'-DDEtetramethy l leadbipheny l
4-bromophenyl pheny l et her3,3'-dichlorobenzidenebenzo [ g,h,i ] pery lenep,p'-DDD
Cl - 1 - PCB average
hept achlor epoxideperylene
benzo [ k ] f luorant henepent achlorophenol
p,p'-DDTtoxaphene
Cl - 2 - PCB averageindeno [ 1,2,3-c,d ] pyrene
2,3,7,8-TCDDdibenz [a,h] anthracene
PeCDD
HpCDDOCDD/FHxCDDCadmiumMercury (I I)HpCDF
HxCDFCl - 10 - PCB
Cl - 9 - PCB averagePeCDF
Cl - 3 - PCB average
octachlorost yreneCl - 8 - PCB average
dinitropyreneCl - 7 - PCB average
Cl - 4 - PCB averageCl - 6 - PCB average
2,3,7,8-TCDFhexachlorocyclohexaneCl - 5 - PCB average
1,4-dichlorobenzene1,2,3,5-tet rachlorobenzene
1,2,3,4- and 1,2,4,5-t et rachlorobenzenepent achlorobenzene
elemental mercuryhexachloro-1,3-butadiene
hexachlorobenzene
0.01 0.1 1 10 100 1000
Approximate Atmospheric Half-Life (Days)
Approximate Atmospheric
Half-Life (Days), based on:
vapor/particle partitioning
vapor-phase rxn with
hydroxyl radical (OH)
dry and wet deposition of
particle-phase and vapor
phase fractions
Typical
atmospheric
“travel distance”
is ~400 km/day,
but this can vary
a lot depending
on the
meteorological
conditions
Consideration of the Exposure
Pathway is Very Important
Inhalation?
Dermal (skin)?
Water?
Food? (and if so, which foods?
This governs what you want to try to find out,
(by modeling, by measurements, or by both)
Mercury transformed by
bacteria into methylmercury
in sediments, soils & water,
then bioaccumulates in fish
Humans and
wildlife affected
primarily by
eating fish
containing
mercury
Best
documented
impacts are on
the developing
fetus: impaired
motor and
cognitive skills
atmospheric
deposition to
the watershed
atmospheric deposition
to the water surface
adapted from slides prepared by USEPA and NOAA
Atmospheric
Models
and
Atmospheric
Measurements
Why do we need atmospheric models?
to get comprehensive source attribution information
...we don’t just want to know how much is depositing at any given
location, we also want to know where it came from: different source regions (local, regional, national, global)
different jurisdictions (different states and provinces)
anthropogenic vs. natural emissions
different source types (power plants, waste incin., smelters…)
Why do we need atmospheric models?
to get comprehensive source attribution information
...we don’t just want to know how much is depositing at any given
location, we also want to know where it came from: different source regions (local, regional, national, global)
different jurisdictions (different states and provinces)
anthropogenic vs. natural emissions
different source types (power plants, waste incin., smelters…)
to estimate deposition over large regions
…because deposition fields are highly spatially variable,
and one can’t measure everywhere all the time…
Why do we need atmospheric models?
to get comprehensive source attribution information
...we don’t just want to know how much is depositing at any given
location, we also want to know where it came from: different source regions (local, regional, national, global)
different jurisdictions (different states and provinces)
anthropogenic vs. natural emissions
different source types (power plants, waste incin., smelters…)
to estimate deposition over large regions
…because deposition fields are highly spatially variable,
and one can’t measure everywhere all the time…
to estimate dry deposition
... presently, dry deposition can only be estimated via models
Why do we need atmospheric models?
to get comprehensive source attribution information
...we don’t just want to know how much is depositing at any given
location, we also want to know where it came from: different source regions (local, regional, national, global)
different jurisdictions (different states and provinces)
anthropogenic vs. natural emissions
different source types (power plants, waste incin., smelters…)
to estimate deposition over large regions
…because deposition fields are highly spatially variable,
and one can’t measure everywhere all the time…
to estimate dry deposition
... presently, dry deposition can only be estimated via models
to evaluate potential consequences of future emissions scenarios
Models are not perfect
“…Everyone believes monitoring results except for the person
making the measurements… and nobody believes modeling
results except for the person doing the modeling…”
How not perfect are they?
Results are encouraging, but difficult to evaluate models due to
lack of contemporaneous monitoring and emissions inventory data
More certain info at a few locations (monitoring)
vs. less certain info region-wide (modeling)
Models are a test of our knowledge…
If they don’t work, fundamental things about our understanding of
atmospheric mercury that are wrong or incomplete…
0
50
100
150
200
250
300
2007.7 2007.8 2007.9 2008 2008.1 2008.2 2008.3 2008.4 2008.5 2008.6 2008.7
RG
M c
on
cen
trati
on
(p
g/m
3)
Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep
2007 2008…. ….
Recent Reactive Gaseous Mercury concentrations at the Grand Bay NERR, MS
Then
down for
~2 months
due to
hurricanes
Air Toxic Phenomena Can be Very Episodic
Environmental Mercury Cycling -- Natural vs. Anthropogenic
Most anthropogenic Hg is “released” as atmospheric emissions:
Hg in coal is released to the air when coal is burned
Hg in other fuels is released to the air when they are processed and burned
Hg in ores is released to the air during metallurgical processes
Hg in products is released to the air when burned or landfilled after being discarded
(e.g., batteries, switches)
This has always been going on, and there has always been Hg in fish
Mercury (Hg) is an element... there is the same amount of mercury on
Earth today as there always has been
“natural” Hg cycle – Hg is transported throughout the environment,
and chemical transformations interconvert different mercury species
But, we make some Hg unexpectedly “bioavailable”
Average, current atmospheric Hg deposition is ~3x pre-industrial levels
Evidence suggests that newly deposited Hg is more bioavailable
Freemont Glacier, Wyoming
source: USGS, Shuster et al., 2002
Natural vs.
anthropogenic
mercury?
Studies show that
anthropogenic
activities have
typically increased
bioavailable Hg
concentrations in
ecosystems by a
factor of 2 – 10
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